Xerographic roller fuser drive apparatus



June 13, 1967 J. R. CASSA'NO ETAL 3,324,791

XEROGRAPHIC ROLLER FUSER DRIVE APPARATUS Filed Dec. 31, 1964 7Sheets-Sheet 1 INVENTORS. R. CASSANO H. TURNER ,JZW

ATTORNEYS JAMES LYMAN June 13, 1967 J. R. CASSANO ETAL 3,324,791

XEROGRAIHIC ROLLER FUSER DRIVE APPARATUS Filed Dec. 31, 1964 7Sheets-Sheet FIG. 9

INVENTORS. JAMES R. CASSANO ATTORNEYS June 3, 96 J. R. CASSANO ETAL3,324,791

XEROGRAPHIC ROLLER FUSER DRIVE APPARATUS Filed Dec. 31, 1964 7Sheets-Sheet Z FIG. 3

INVENTORS. JAMES R. CASSANO LYMAN H TURNER ATTORNEYS June 13, 1967 J. R.cAssANo ETAL 3,3

XEROGRAPHIC ROLLER PUSER DRIVE APPARATUS '7 Sheets-Sheet Filed Dec. 31,1964 0 R N P ms v wt M R6 v R R m3 5 vww F m J m3 wum 8% mg m .9% mam E.B 1 1 I 1 8% WW m 3; Sn 3m 3m mmm mmm kw Mm A/mmw nix I T 9% MG Wlwwm mh ||&m mm Q% I O a: V\W x u F own mm Gm 8? km a m. mkm fin Pa 1 IHHWHHHHWH UHHHHHWUHHH mmn A Km 7% a 3mm N K T m mun mm 9% A N kw. Gm m%m 9% 5.6 mm %m Em Mk wk B LYMAN H. TURNER ATTORNEYS 7 Sheets-5heet June13, WW? J. F2. cmsssmwz: ETAL XEROGRAPHIC ROLLER FUSBH DRIVE APPARATUSFiled Dec. 31, 196

June 13, 1967 .1. R. CASSANC) ETAL 3,324,791

XEROGRAPHIC ROLLER FUSER DRIVE APPARATUS Filed Dec. 31. 1964 t 7Sheets-Sheet a s 5 0 k) g .1: Q J

INVENTOR& I

JAMES R. CASSANO ymm H. TURNER ATTORNEYS June 1967 .J. R. CASSANO ETAL3,324,791

XEROGRAPHIC ROLLER FUSER DRIVE APPARATUS Filed Dec. 31, 1964 7Sheets-Sheet 7" FIG /0 INVENTORB. JAMES R. CASSANO gLYM AN Hg. TURNERATTQWEY$ United States Patent 3,324,791 XEROGRAPHIC ROLLER FUSER DRIVEAPPARATUS James R. Cassano, Rochester, and Lyman H."Ihrner, Pittsford,N.Y., assignors to Xerox Corporation, Rochester, N.Y., a corporation ofNew York Filed Dec. 31, 1964, Ser. No. 422,727 1 Claim. (Cl. 100-172)This invention relates to improvements in heat fusing devices and,particularly, to an improved apparatus for fiXing xerographic powderimages.

More specifically, the invention relates to an improved heated-rollfusing device. Although the invention is considered to havegeneralapplication, it is particularly useful in the field of xerographyand has an important application in the fusing of resinous powder imagesproduced by electrophotography or xerography onto sheets of paper andthe like to which the powder images have been transferred after theyhave been formed by deposition of powder on an electrostatic latentimage. Therefore, for convenience of illustration, the invention isdescribed with reference to its use as a heat fuser for xerographicpowder images. However, it is to be understood that it may be employedwith equal facility in other fields.

In the process of xerography, for example, as disclosed in CarlsonPatent 2,297,691, issued Oct. 6, 1942, a xerographic plate, comprising alayer of photoconductive insulating material on a conductive backing, isgiven a uniform electric charge over its surface and is then-exposed tothe subject matter to be reproduced, usually by conventional projectiontechniques. 'This exposure discharges the plate areas in accordance withthe radiation intensity that reaches them, and thereby creates anelectrostatic latent image on or in the photoeonductive layer.Development of the latent image is effected with an electrostaticallycharged, finely divided developing material or toner which is broughtinto surface contact with the photoconductive layer and is held thereonelectrostatically in a pattern corresponding to the electrostatic latentimage.

Thereafter, the developed xerographic powder image is i usuallytransferred to a support surface such as paper to which it may be fixedby any suitable means.

One of the methods in common-use for developing the electrostatic latentimage is described in Walkup Patent 2,618,551 and is known as cascadedevelopment, and is in general use for line copy development. In thistechnique, the powder or toner is mixed with a granular carriermaterial, and this two-component developer is poured or cascaded overthe plate'surface. The function of the'carrier material is to improvethe'flow characteristics of the powder and to produce, on the powder, bytriboelectrification, the proper electrical charge so that the powderwill be attracted to the image. More exactly, the function of thecarrier material is to provide the mechanic-al control to the powder, orto carry the powder to an image surface and, simultaneously, to providehomogeneity of charge polarity.

In the Carlson patent it is noted that a variety of types of finelydivided electroscopic powders may be employed for developingelectrostatic latent images. However, as the science of xerography hasprogressed, it has been found preferable to develop line copy imageswith a powder or toner formed of any of a variety of pigmentedthermoplastic resins that have been specifically developed for thepurpose. A number of such developing materials are manufactured andmarketed commercially and are specifically compounded for producingdense images of high resolution and to have characteristics to permitconvenient storage and handling. Such developing materials arecompounded to permit them to be fixed tothe surface 3,324,791 PatentedJune 13, 196' of a transfer material either by heat fixing or vaporfiXlIl) techniques, in accordance with the particular applicatio; inwhich they are employed, that is, the individual parti cles of resin(toner) soften and coalesce when heated 0 plasticized by solvent, sothat they become sticky o tackified and readily adhere to the surface ofthe suppor material.

The term tackified and the several variant form: thereof used throughoutthis specification are employer to define the condition of the powderparticles of 'tht xerographic powder image when heated or plastlcizedla; a solvent in a manner such that the individual particle: soften andcoalesce and in which state they become sticky and readily adhere toother surfaces. Although this condition necessarily requires a flowingtogether of the particles to effect a thorough fusion thereo, it is tobe understood that the extent of such flowing is not suflicient toextend beyond the boundary of the pattern in which the particles areformed.

One of the important applications of the process of xer-ographycomprises its use in automatic copying machines for general oflice usewherein the powder images formed on a xerographic plate are transferredto paper and then fixed there-on by heat fusing. In order to fuseresinous powder images formed of the powdered resins now commonly used,it is necessary to heat the powder and the paper to which it is to befused to a relatively high temperature, such as approximately 325 F. Itis undesirable, however, to raise the temperature of the papersubstantially higher than 375 F. because of the tendency of paper todiscolor at such elevated temperatures.

It has long been recognized that one of the fastest and most positivemethods of applying heat for fusing the powder image to paper is tobring the powder image into direct contact with a hot surface, such as aheated flat plate.

But, as the powderima-ge is tackified by heat, part of the image carriedby the support material will stick to the surface of the heated plate,so that as the next sheet is placed on the heated plate, the tackifiedimage partially removed from the first sheet will partly transfer to thenext sheet and, at the same time, part of the tackified image from saidnext sheet would adhere to the heated plate. This process is commonlyreferred to in the printing art as set off or oifsetf, the latter termbeing preferred.

The offset of toner onto the heated contacting surface has heretoforeled to the rejection of contact fusers in favor of other heat fixingdevices, primarily coiled radiant element heaters with reflectors. Theseradiant element heaters with reflectors have the disadvantaged d-iSSlrpating a large quantity of heat into themachine enclosure in which theyare used, heat transfer to the powder image is ineflicient, and theypresent a safety hazard because of the exposed radiant element. I t

' It is, therefore, the principal object of this invention to improvethe construction of a direct contact fusing devicefor toner images whichwill rapidly fuse toner images without causing the toner particles tosmear while in a tackified state of to offset onto the device.

This and other objects of the inventionare attained .by means ofa directcontact fusing device in which the toner image is fused byforwarding thesheet or web of paper to be read in connection with the accompanyingdrawings, wherein:

FIG. 1 illustrates schematically the preferred embodiment of axerographic reproducing apparatus adapted for automatic operation, andincorporating a roller heat fuser constructed in accordance with theinvention;

FIG. 2 is an isometric view of the heat fuser assembly and drivetherefor;

FIG. 3 is a top view of the fuser assembly with parts broken away toshow details of the fuser rollers and supports;

FIG. 4 is a side sectional view of the fuser assembly with parts brokenaway to show the structure of the fuser rollers;

FIG. 5 is a rear view of the fuser assembly;

FIG. 6 is a sectional view of the fuser assembly taken .along line 66 ofFIG. 3, with parts broken away to show details of the upper fuser rolland applicator roll;

FIG. 7 is a front view of the fuser assembly;

FIG. 8 is a sectional view taken along the line 8-8 of FIG. 3;

FIG. 9 is a diagrammatic illustration of the upper and lower fuserrollers when pressure is applied thereto; and

FIG. 10 is a schematic view of a drive system for use with the fuserassembly.

Although it forms no part of the subject invention, there is shownschematically in FIG. 1 a continuous xerographic apparatus for thepurpose of illustrating a suitable environment for the heat fuser of thesubject invention.

As shown schematically in FIG. 1, the automatic xerographic reproducingapparatus comprises a xerographic plate 14 including a photoconductivelayer or light-receiving surface on a conductive backing and formed inthe shape of a drum, which is mounted on a shaft journaled in frame torotate in the counter-clockwise direction to cause the drum surfacesequentially to pass a plurality of xerographic processing stations.

For the purpose of the present disclosure, the several xerographicprocessing stations in the path of movement of the drum surface may bedescribed functionally as follows:

A .charging station, at which a uniform electrostatic charge isdeposited on the photoconductive layer of the xerographic drum; Anexposure station, at which a light or radiation pattern of copy to bereproduced is projected onto the drum surface to dissipate the drumcharge in the exposed areas thereof and thereby form a latentelectrostatic image of the copy to be reproduced;

A developing station, at which a xerographic developing materialincluding toner particles having an electrostatic charge opposite tothat of the electrostatic latent image are cascaded over the drumsurface, whereby the toner particles adhere to the electrostatic latentimage to form a xerographic powdered image in the configuration of thecopy being reproduced;

A transfer station, at which the xerographic powder image iselectrostatically transferred from the drum surface to a transfermaterial or support surface; and

A drum cleaning and discharge station, at which the drum surface isbrushed to remove residual toner particles remaining thereon after imagetransfer, and at which the drum surface is exposed to a relativelybright light source to effect substantially complete discharge of anyresidual electrostatic charge remaining thereon.

As shown, the charging arrangement includes a corona charging device 15which includes a corona discharge array of one or more corona dischargeelectrodes that extend transversely across the drum surface and areenergized from a high potential source and are substantially closedwithin a shielding member.

Next subsequent thereto in the path of motion of the xerographic drum isan exposure station. An optical scanning or projection system isprovided to project a flowing imageonto the surface of thephotoconductive drum from a moving original.

The optical scanning or projection assembly may comprise a minified datacard projection system 11 which is adapted to scan individual data cardswith a light line and project the image rays onto the movinglight-receiving surface of the xerographic drum. The scanning light may'be provided by a suitable light source arranged to scan a minified datacard. The data card image rays are directed through a lens 12 onto thexerographic drum through a slot in a fixed light shield 13 positionedadjacent to the xerographic drum surface.

Adjacent to the exposure station is a developing station A in whichthere is positioned a developer apparatus 11 including a casing orhousing having a lower or sump portion for accumulating developermaterial. A bucket type coveyor is used to carry the developing materialto the upper part of the developer housing where it is cascaded over ahopper chute onto the xerographic drum to effect development.

Positioned next and adjacent to the developing station is the imagetransfer station B which includes a sheet feeding arrangement adapted tofeed sheets of support material, such as paper or the like, successivelyto the xerographic drum in coordination with the presentation of thedeveloped image on the drum surface at the transfer station. I The sheetfeeding mechanism includes a sheet feed de vice 18 adapted to feed thetop sheet, of a stack of sheets on a tray 20, to feed rollers 280, 281which arrests and aligns each individual sheet of material and then intimed relation to the movement of the xerographic drum, advances thesheet material into contact with the xerographic drum in registrationwith a previously formed xerographic powder image on the drum.

The transfer of the xerographic powder image from the drum surface tothe sheets of support material is effected by means of a corona transferdevice 21 that is located at or immediately after the line of contactbetween the support material and the rotating drum. In operation, theelectrostatic field created by the corona transfer device is effectiveto tack the support material electrostatically to the drum surface,whereby the support material moves synchronously with the drum while incontact therewith. Simultaneously with the tacking action, theelectrostatic field is effective to attract the toner particlescomprising the xerographic powder image from the drum surface and causethem to adhere electrostatically to the surface of the support material.

Immediately subsequent to the image transfer station, there ispositioned a stripping apparatus to paper pick-off mechanism 22 forremoving the sheets of support material from the drum surface. Thisdevice may be of the type disclosed in Rutkus et al. United StatesPatent 3,062,536 for stripping the leading edge of the sheet from thedrum surface and to direct it onto an endless conveyor 24 whereby thesheet material is carried to a fixing device 25, the subject matter ofthis invention. At the fixing device, the transferred xerographic powderimage on the sheet of support material is permanently fixed or fusedthereto as by heat. After fusing, the reproduction is discharged fromthe apparatus at a suitable point for collection externally of theapparatus by means of the conveyor 26. In the embodiment shown, thereproductions are discharged from conveyor 26 into a receiving tray 495.

The next and final station in the device is a drum cleaning station C,having positioned therein a corona preclean device 27 to remove anypowder remaining on the xerographic drum after transfer.

It is believed that the foregoing description is sufficient for thepurposes of this application to show the general operation of axerographic reproducing apparatus using a roller fusing deviceconstructed in accordance with the invention. For further detailsconcerning the specific construction of the xerographic apparatus andthe data card handling apparatus 11, reference is made to copendingapplication Sek No. 422,804 filed concurrently herewith on Dec. 31,1964, in the name of Hewes et al.

Referring now to the drawings, there is shown a preferred embodiment ofa heated roller fusing apparatus 25 constructed in accordance with theinvention.

As shown in FIGS. 2-9, the fuser apparatus 25 is of the heated rollertype and includes a frame for supporting the upper roller of the fuserapparatus formed by spaced apart end plates 550, 551 held in spacedrelation by two lower braces 552, 553 and two upper braces 554, 555. Thefour braces, more or less are secured to the four corners of each of theend plates thereby forming a generally rectangular frame for the fuserstructure. The lower fuser roller is supported in a position parallel tothe upper roller by this frame.

Direct contact fusing of a powder image on a sheet of paper supportmaterial is achieved by forwarding a sheet of the support materialbearing the powder image to be fused between a heated upper roller,generally designated 556, and an unheated lower roller, generallydesignated 557, rotating in intimate contact under pressure during afusing operation. The support material carrying the unfused tonerimages, is advanced between these two rollers with the toner imagesfacing the heated roller so that fusing occurs when contact is made.

As shown in FIG. 4, the upper roller 556 includes a cylinder 558 partlyclosed at opposite ends by right-hand and left-hand fuser roller caps560 and 561, respectively, which are secured to the cylinder, as by apress fit. The caps 560, 561, are formed with tubular shanks 562, 563,respectively, which extend outwardly from the cylinder 558. The rolleris journaled for rotation by bearings 564 and 565 which encircle theshanks 562, 563 and are positioned in the frame plates 550 and 551,respectively.

The inner race of the bearing 564 is secured between a shoulder on theshank 562 and a thrust washer 566 held against this race by a retainingring 567. The outer race is secured to the plate 550 by means of thering 567 and an inner ring 570 which are held to the plate 550 by screws568. The grooved races closely encompassing portions of the bearingballs maintain the axial relationship between the races and thus locatethe roller 556 relative to the fuser assembly frame.

On the opposite end of the roller, the inner race of the bearing 565 islocked against inward movement by a thrust washer 571 secured in asuitable groove formed inwardly on the shank 563. The inner and outerraces of the bearing 565 are free to move slightly during expansion ofthe roller 556 when heated but are prevented from removal from the frameplate 551 by a retaining ring 572 secured by screws 573 to the outersurface of frame plate.

Each of the fuser roller caps is provided with a suitable aperture toreceive a quartz tube 574 which supports a resistance heating elementR-1. The ends of the resistance element R-l project through the shanks562, 563 and terminate in terminals 575 which may be connected bysuitable conductors to a source of power. Insulating caps 576, securedto the plates 550, 551 by the rings 567, 572, respectively, are providedbetween the terminals and the frame plates to prevent dust or dirt fromentering the bearings 564, 565 and to prevent inadvertant electricalarcing. The caps 576 are formed with cavities for accommodating andsupporting the ends of the quartz tube 574, which is stationary whilethe roller 556 rotates. A thermistor THS-Z part of a suitable electricalcontrol system for controlling power to the resistance element R-l, issuitably positioned in thermal relation to the fuser roller 556. Detailsconcerning the electrical control circuit for the fuser are notnecessary for the present invention. Any suitable circuit may beutilized to attain this end, such for example, the circuit described inthe above referred to patent application of Hewes et al.

To prevent toner offset onto the heated roller contacting the unfusedtoner image on the support material, an

offset preventing material 577 covers the outer surface cylinder 558 ofthe roller 556. A suitable material may b a coating of a product oftetrafiuorethylene resin sol under the trademark of Teflon :by the DuPont Corporz tion.

The upper roller 556 is driven in direct relation by th lower roller 557by means of gears, one secured to eacI of these rollers. Between thebearing 565 and the left hand cap 561 for the upper roller, a gear 578is secure by suitable screws 579 to the cap, and this gear is operatively engaged with a gear 581 secured to the suppor shaft 582 for thelower roller 557.

The lower roller 557 includes a rigid core 583 covere with a suitableresiliently deformable material 584, sucl as silicone rubber, which, inturn, is covered by a Teflor coating 585. The Teflon coating deformswith the rubber 583 in relation to the amount of pressure betweenheatec' roller 556 and the roller 557 to form an arc of contac' forproper fusing of the thermoplastic resin on the support material. Thecoating provides a protective covering on the material 584 to preventdeterioration of the rubber due to heat and/or contact with offsetpreventing liquid, the application of which is to be hereinafterdiscussed.

The roller 557 is rotatably supported on the support shaft 582 byleft-hand and right-hand bearings 586 and 587, respectively. The innerrace of right-hand bearing 587 is held against outward axial movementrelative to the shaft 582 by a ring 588 while the outer race is heldagainst movement by a retaining ring 590 secured in a suitable grooveprovided in the outer race and secured by suitable screws to an uprightplate 591. The inner race of left-hand bearing 586 is held againstoutward movement relative to the shaft by a retaining ring 592 securedin a groove provided in the shaft, and its outer race is held by anupright plate 593 but is allowed to move axially due to expansion ofmetal parts when heated. The gear 581 for rotating the roller 557 issecured to the left-hand side of the shaft 582 by a suitable set screw(not shown) to enable the roll to be driven in a manner to be described.

The upright plates 591, 593, as shown in FIG. 8, are triangular in shapewith one apex being formed with an aperture for accommodating bearings586, 587 and through which the shaft 582 extends. Another aperture isformed on each of these plates at a second apex arranged horizontallyrelative to the shaft 582 and through these apertures a shaft 594projects. The shaft 594 is mounted in the frame plates 550, 551 forsupport thereat and permits limited rotative movement of the plates 591,593 about its axis.

The plates 591, 593 which support the shaft 582 for the lower roller 557are formed at their lower apexes with apertures through which extendbushings 597, 598 secured therein and which rotatably support pins 600,only one of which is shown in FIG. 4. At the inner ends of the pins 600,but on the other side of the plates 591, 593, are secured circularrollers 601, 602 which cooperate with cam rollers 603, 604,respectively, mounted on a cam shaft 605 which is rotatably mounted onthe frame for the fuser assembly. The cam rollers 603, 604 are arrangedeccentrically relative to the axis of the cam shaft 605 and when rotatedby this shaft force the coacting follower rollers 601, 602,respectively, upwardly slightly to rotate each of the plates 591, 593about the axis of the support shaft 594 for these plates. This actionserves to raise the lower roller 557 into a cooperating position withthe heated ro1ler 556 once for each partial revolution of the shaft 605for fusing toner particles onto a sheet of copy paper as it travelsbetween the rollers 556, 557 or to lower the lower roller out of contactwith the heater roller when there is no sheet therebetween. The rollers601, 602 are described as circular; however, these may be arrangedeccentrically relative to their respective pins 600 for the purpose ofpresetting the maximum spacing between the 7 )llers 556, 557. A screw606 may be provided in each f the pins 600 to effect this adjustment.

The roller 557 is raised into pressure contact with the eater roller 556by operation of a differential drive iechanism generally indicated bythe reference numeral 10 which serves to drive the lower roller andconseuently, the heater roller. To this end, the mechanism 10 isprovided with a timing gear 611 rotatably mounted t one end of the shaft605. A timing belt 612 is arranged round the gear 611, an idler gear 613and, a driven gear 14 secured to the extreme end of the lower rollershaft $82. Also rotatably mounted on the shaft 605 in axial .lignmentwith the gear 611 is a drive gear 615 which is ecured to the timing gear611 by a set screw 616. With his arrangement it will be apparent thatrotation of the frive gear 615 about the shaft 605 will impart rotation)f the lower roller 557.

Another gear 617 is also rotatably mounted on the ihaft 605 and islocated toward the extreme end thereof .n relation to the drive gear615. The extreme end of the ;haft terminates in an aperture formed in asupport plate 618 and is fixed thereto by a set screw 620. A firstplanetary gear 621 is supported for rotation inwardly and upwardly ofthe support plate 618 and a pivot pin 622 and is in mesh with the gear617. A second planetary gear 623 is supported for rotation inwardly anddownwardly of the support plate by a pivot pin 624 and is in mesh withthe gear 621 immediately above it and with the drive gear 615.

In the arrangement of the differential mechanism 610, thus fardescribed, the drive gear 615 and the gear 617 serve as the sun gearsfor the planetary gears 621 and 623. Means are provided for rotating thegear 617, as will be described hereinafter, in order to initiate actionand coaction in the fuser assembly. In utilizing the differentialcharacteristics of the gear assembly, it is required that the total ofthe frictional forces developed between the rollers 556 and 557 andtheir respective bearing supports, the inertia these elements producetogether with the inertia and friction encountered with the timing belt612 and the timing gears 611, 613 and 614 is greater than the totalfrictional forces produced by the rotation of the gears 621, 623 upontheir respective pivots combined with the friction developed by therotation of the gear 617 upon the shaft 605 and the interaction betweenall the gear teeth involved. With this condition, rotating the gear 617by an external device will cause rotation of the gear 621 to meshtherewith which will cause rotation of the gear 623. This latter gearbeing in mesh with the drive gear 615 will cause the plate 618 and thetwo gears 621, 623 to orbit about relatively fixed sun gears 615 and 617since the force necessary to produce this orbiting action is less thanthe force required to rotate the gear 615, as pointed out above. Thisorbiting motion about the axis of the shaft 605 will start from theposition shown in FIG. 5 and will result in movement of the plate 618and gears 621, 623 in the direction of the arrow until the edge of theplate 618 is stopped by a screw stop 625.

This movement of the plate 618, in turn, produces corresponding rotationof the shaft 605 which, for the arrangement shown, may rotate forapproximately 100. With the stop 625 being in the form of an adjustingscrew, the amount of rotation can be varied. As the shaft 605 rotates,it rotates the eccentric surfaces 603, 604 which action forces the camfollowers 601, 602 upwardly for raising the lower roller 557 intocontact with the heater roller 556. The degree of force can be varied bythe positioning of the adjusting screw stop 625 which limits the amountof camming provided by the cams 603, 604.

With the rollers 556, 557 forced into contact and with the plate 618 nowheld against further rotation, continued rotation .of the gear 617 willimpart rotation to the drive gear 615 through the planetary gears 621,623. Rotation of the gear 615 will impart the same motion to the timingdriven gear 611 for driving the lower roller 557 which drive willproduce rotation of the roller 556 by means of the gears 578, 581. Afterthe external drive means is no longer effective to rotate and hold thegear 617, the shaft 605 is rotated in the opposite direction to bringthe parts of the differential mechanism into their positions, as shownin FIG. 7 by a helical spring 626 secured at one end to the other end ofthe shaft 605 and at its other end to an anchor 627 mounted on the frameplate. During rotation of the shaft 605 for imparting upward movement ofthe lower roller 557, the spring 626 will wind up slightly to producespring tension on the shaft which tension is released to rotate theshaft in an opposite directionto bring the parts of the differentialmechanism to their original positions.

The external drive means for imparting the rotative force to the gear617 is derived from a drive mechanism illustrated in FIG. 10.Immediately above the gear 617 and in mesh therewith is a drive gear 630secured to the drive shaft SH16 and encircled by a drive sleeve 631. Theshaft and sleeve are mounted on a post 632 which is part of the mainmachine frame and which may extend !upwardly from the base thereof. Aswill be described here-' inafter, the fuser assembly 25 is movable as aunit into and out of the machine frame and, when moved into itsoperating position, will permit the meshing engagement of the gear 630with the gear 617.

On the end of the sleeve 631, remote from the drive gear 630, there issecured a large gear 633 which is in' operative engagement with anotherlarge gear 634 attached to one end of the shaft SH17. This shaft ismounted for rotation on an upwardly extending post 526 secured to themachine base and has secured thereto at its other end the pulley 527. Adrive belt 528 is arranged around the pulley 527 a main drive pulley 483and an idler 635 rotatably mounted on a shaft SH13 which is suitablymounted on the machine frame. The main drive motor M2 which may beutilized to drive the dnum 14 serves to impart continuous rotation tothe large gear 633 and thereby maintain continuous rotation of the drivesleeve 631. As shown in FIG. 10, the sleeve 631 is open adjacent thegear 617 and may be suitably supported at this end by a bearing (notshown).

The end of the shaft SE16, remote from the gear 630, has secured theretoa magnetic clutch member 636 in the form of a disc which is rotatablymounted with an annular groove 637 formed in the rear frame plate forthe machine. Within the groove 637 and lining the walls thereof is anannular channel member 638 in which the clutch member rotates.Preferably, the clutch member and the channel member are made of highlymagnetizable material in order to produce strong magnetic lines whenenergized with DC. potential. Suitable conductors may be provided forconnecting the channel to a source of DC. potential, such as arectifier, and be arranged so that the clutch member 636 will beenergized whenever the main drive motor M2 is energized.

A second clutch member 639 in the form of a disc, serving as anarmature, is secured to one end of the drive sleeve 631 in closeface-to-face relationship to the clutch member 636. When energized byDC. potential, the clutch member 636 will produce magnetic lines offorce and be attracted to the clutch member 639. Normally, the member636 and the shaft SH16 are stationary while the disc 639 continuouslyrotates. With magnetic lines of force existing between the members 636and 639, the member 636 will rotate in unison with the member 639 forestablishing movement of the lower roller 557 into forced engagementwith the upper roller 556 and rotation of these rollers for fusingimages on sheets of copy material.

In actual practice, during operation of the xerographic machine when themain motor is continuously in operation, the clutch member 639continuously drives the clutch member 636 resulting in the continuousrotation of the rollers 556, 557. When the machine is not in runningcondition or is in standby condition, the circuit to the clutchmechanism is open and the fuser assembly is not operating. In addition,during standby condition, when the fuser is not operating, the rollers556 and 557 are automatically separated. This separation, when therollers are not rotating prevents thermal set of the rubber in theserollers.

A supply of silicone oil to be applied to roller 557 is maintained in anoil pan 640 having fastened to opposite ends thereof bracket means 642by which the oil pan is mounted on the frame plates. An applicator roll643 is used to convey a thin film of oil as the applicator roll isrotated in the silicone oil, to wick 644, such as a felt pad secured asby staples (not shown), to a wick support plate 645 in a manner wherebythe pad rests on the peripheral surface of the roller 556 and theapplicator roll 643. The wiper plate is curved at one end to conform tothe peripheral surface of the roller 557.

The applicator roll 643 consists of a hollow cylindrical oil drumsupported at opposite ends by caps 646 and 647. At one end, the oil drumis secured by the cap 647 on a hollow shaft 648, which is jo-urnaled forrotation in a bracket 650 supported in the fuser assembly and issupported at the other end by a bearing 651 mounted for rotation in abracket 652. A compression spring, not shown, is axially supportedwithin the shaft 648 between bracket 650 and the cap 647 to facilitatereplacement of applicator roll 643, the spring normally biasing theapplicator roll to the left as shown in FIG. 3.

To effect rotation of the applicator roller in one di-' rection, theroller is driven by a one-way clutch, (not shown) enclosed within thehollow shaft 648. A control arm 653 is secured to the shaft 648 forintermittently rotating the roller 643 a few degrees for every rotationof the heated roller 556. The control arm 653, driving the one-wayclutch mechanism within the shaft 648, is provided with a depending camsurface portion adapted to be engaged when each of a plurality of anactuator studs 654 extending outward from the gear 578 for the upperroller 556 is rotated into contact therewith. A tab 655 formed on thecontrol arm 653 is biased into contact with an adjustable screw 656fastened to frame plate 551 of the fuser assembly, by a spring 657secured to the control arm 653.

The amount of intermittent rotation of the applicator roller may beregulated by adjustment of the positioning of the screw 656 in a slot658 which controls the arc of travel of the control arm governing theone-way clutch mechanism within the shaft 648. With this arrangement, asthe upper heated roller 556 is rotated by means of the drive mechanismpreviously described, the actuator studs 654 will successively strikethe cam surface portion of the control arm to cause the control arm tooscillate about the axis of applicator roller during rotation of theupper roller 556. In this manner, the applicator roll is indexed, aportion of a revolution during each oscillating cycle of the control arm653 through the one-Way clutch drive between the applicator roller andthe control arm.

During operation of the fuser assembly, the rollers 556 and 557 mustmaintain identical velocity at their point of contact at all times whena powdered image is being fused on a sheet of copy paper. This isnecessary to prevent tearing the copy sheet or distorting the image onthe support material. As shown in FIG. 9, the outer diameters of therollers, when not in contact are equal and since both of the rollers aredriven by gears having equal diameters, the lineal speed is the samewhen these rollers are merely in touch contact or out of contact.However, when pressure is applied to the lower roller 557 forcing itinto contact with the heated roller 556, the distance between thecenters of these rollers decreases. The radius R from the center ofroller 556 to its point of contact with roll 557 remains fairly constantowing to the metallic cylinder 558 for which the roller is provided tofacilitate the radiation of heat from the heater element R1 to thecovering 577. The radius R of the roller 557,

It) from its center to point of contact with roll 556, is decreased dtueto the pressure upon the resilient material 584 to provide an arc M ofcontact to assure proper fusing.

If the angular velocities of the rollers are the same, this differencein radii would result in a differential lineal velocity at the point ofcontact with the periphery of the upper roller 556 traveling faster thanthe periphery of the lower roller with the resultant smearing of thetackified image and the possible tearing of the copy sheets.

In order to prevent any differential in lineal velocity at the point ofcontact of the rollers, an overriding clutch 660 is provided on theshaft 582 for the lower roller 557. The driven portion of this clutch isfixed to the core 583, and the driving portion is secured to the shaft582 which is driven at a constant speed by the differential mechanism610. By the use of overriding clutch or one way clutch 660 to drive theroller 557, the roller is free wheeling in one direction relative to thedriving shaft 582 for the roller; that is, the one-way clutch allows thelower roller to run at a greater speed than its driving member, theshaft 582. This increase in speed is caused by the upper roller 556which, when there is a sheet of papers between the rollers, producessufficient friction between the rollers to drive the lower surface whilethese rollers are in contact. During this phase of operation, the shaft582 continues to drive the gears 581 and 578 at its original constantvelocity and the heater roller 556 maintains constant velocity. With theslight compression of the coating 585 and the resilient material 584 inthe lower roller existing at this time, the lower roller will experiencea slight increase in speed in order to maintain the constant linealspeed at the point of contact for the rollers. This action will cause aslight overriding of the lower roller upon its shaft 582 made possibleby the one-way clutch mechanism provided between the driving shaft andthe driven lower roller.

As a sheet of copy paper is advanced between the rollers 556, 557, thepowder image on the copy sheet will contact the peripheral heatedsurface of the roller 556 whereby the powder image becomes tackified.The application of the silicone oil from the oil pan 640 upon the Tefloncoating 577 will prevent the offset of the toner material onto theheated contact surface of the heated roller.

After the powder image has been fused upon the sheet of copy paper, thesheet is transported by action of the rollers 556, 557 out of the fuserassembly, through the guide plates 518 and into engagement with the feedrollers 520 of the vertical transport system 26 to be conveyed out ofthe machine as previously described.

The fuser assembly 25 is also provided with means for permitting easyand complete removal of the assembly as a unit from the machine. To thisend, each of the lower braces 552, 553 has secured thereto the innerrace 662 of a commercial type file cabinet drawer slides. Each of theouter races 663 for the slides are attached to a support member 664which extend across the entire length of the fuser assembly and aresecured in parallel arrangement to the base of the machine. Suitableball-bearings mounted between the races 662, 663 permit slidable actionbetween the fuser assembly and the machine and removal of the assemblytherefrom. Means (not shown) may be provided for locking the assembly inits operating position wherein the driven gear 617 on the assembly is inmesh with the driving gear 630.

While the invention has been described with reference to the structuredisclosed herein, it is not confined to the details set forth, and thisapplication is intended to cover such modifications or changes as maycome within the purposes of the improvements or the scope of thefollowing claim.

What is claimed is:

A drive mechanism for contact fusing resin material carried on a supportmaterial, such as sheets of paper, said mechanism including:

a casing,

a first roller mounted on a shaft journalled in said casa second rollerhaving a shaft journaled for rotation and movement from a first positionwherein said second roller is out of contact with said first roller andto a second position wherein said second roller is in cooperatingpressure contact with said first roller,

actuator means connected to said second roller for moving said rollerfrom said first position wherein said roller is out of operativerelation with said first roller to said second position wherein saidsecond roller is in cooperative relation to said first roller,

drive means having a drive gear,

a differential gear set having first and second sun gears, planet gearsconnected therebetween and a frame for rotatably supporting the gears,

said first sun gear engageable with said drive gear and,

during operation of said drive means, being adapted initially to producerevolution of the planet gears and the frame and to produce rotation ofthe second sun gear when the frame is held against revolving action,

a drive train operatively connecting the shaft of the second roller tosaid second sun gear,

said frame being connected to the actuator means and adapted to actuatethe same for moving the second roller to the second position when theframe revolves about said first sun gear,

and means for limiting the revolution of said frame during operation ofsaid drive means whereby the frame is held against further revolvingaction to permit rotation of the second roller while in said second.position.

References Cited UNITED STATES PATENTS 1,817,604 8/1931 Behan 682581,820,032 8/1931 Roberts 68253 2,214,095 9/1940 Watts 68253 2,268,8291/1942 Kautfman 68258 2,766,604 10/1956 Thiele 68253 LOUIS O. MAASSEL,Primary Examiner.

